Anti-settling agents are used in the coatings industry to prevent pigments or other finely divided solid particles from settling during storage. Anti-settling agents can be categorized as organic clay, polyamide, ethylene vinyl acetate polymers, fumed silica and calcium sulfonate derivatives. Many of these anti-settling agents, however, have their drawbacks. For example, organic clay and fumed silica can negatively impact the coatings in which they are applied through gloss decrease and increase of viscosity of the paint, significantly affecting flow and leveling of the paint.
Anti-settling agents in a coating formulation requires additives which generally maintain the proper viscosity of the coating formulation. This is sometimes difficult, as, for example, better control pigment dispersion or settling means generally higher viscosities. Coating compositions with extremely high viscosities just after application may negatively affect flow rates where, as a consequence, low flow rates occur and hinder the formation of a smooth film.
Conventional natural and synthetic polymers have limitations with respect to use as thickeners in aqueous systems, particularly in paints and coating compositions. In general, they do not provide a rheological profile suitable for the desired flow and other properties required in paints and coatings. For example, HEC swells rapidly in water and forms lumps, which are not readily dispersible. A correct balance of properties must be achieved among the various additives.
Thickeners are used in paint to achieve particular rheological properties such as the shear-rate-dependent behavior, to control the viscosity at low, medium and high shear rates, sag resistance and application viscosity. A type of associative thickener commonly found in latex paints is known as hydrophobically-modified alkali-swellable emulsion (HASE) polymer. These HASE polymers are carboxyl functional polymers synthesized by free radical polymerization. HASE polymer systems can be prepared from the following monomers: (a) an ethylenically unsaturated carboxylic acid, (b) a nonionic ethylenically unsaturated monomer, and (c) an ethylenically unsaturated hydrophobic monomer.
HASE thickeners are based on a polyelectrolyte backbone, usually methacrylic acid and ethylacrylate copolymer, with pendant hydrophobes (i.e., hydrophobes attached to the backbone with polyethylene oxide chains). When neutralized with a suitable base, carboxylic acid groups along the polymer backbone are ionized to yield water-soluble polymers. The dissolution of particles results in changes in polymer conformation and solution rheology. A number of factors contribute to the thickening effect of HASE polymers: association of hydrophobic groups, topological entanglements, and chain expansion of high molecular weight polyelectrolyte backbone.
Representative HASE copolymer systems include those shown in EP 226097 B1, EP 705852 B1, U.S. Pat. No. 4,384,096, U.S. Pat. No. 5,874,495, U.S. Pat. No. 7,217,752 B2, and US Patent Application Publication 2006/0270563 A1, now U.S. Pat. Nos. 7,772,421 and 8,071,674, and US Patent Application Publication 2012/0123149 to Yang et al, all incorporated herein by reference.
Three categories of polymers produced by emulsion polymerization are: (1) Synthetic rubber: some grades of styrene-butadiene (SBR), some grades of polybutadiene, polychloroprene (Neoprene), nitrile rubber, acrylic rubber, fluoroelastomer (FKM); (2) Plastic: some grades of PVC, some grades of polystyrene, some grades of PMMA (polymethylmethacrylate), acrylonitrile-butadiene-styrene terpolymer (ABS), polyvinylidene fluoride, polytetrafluoroethylene (PTFE); and (3) Dispersions (i.e., polymers sold as aqueous dispersions).
Latex is an example of an emulsion polymer which is a water based polymer dispersion. Latex paints are used for a variety of applications including interior and exterior, and flat, semi-gloss and gloss applications. Latex is a stable dispersion (colloidal emulsion) of rubber or plastic polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.
In spite of their many important advantages, HASE thickeners are inherently more sensitive to variations in coating composition. HASE thickeners interact with surfactants present in paint formulations and such interaction result in a large viscosity loss. Due to the interaction with surfactants they require more attention in formulating. Paints thickened with HASE rheology modifiers are also more sensitive to the addition of tinting colorants which contain surfactants and/or dispersants which can result in large viscosity drops. Often, a consequence of this viscosity loss is inferior application properties such as poor films build, sagging and severe color float.
As tinted and colored paints become more popular, the need for rheology modifiers that can withstand the addition of colorants without significant viscosity loss has gained in importance.
Hydraulic fracturing of the subterranean formation is conducted to increase oil and/or gas production. Fracturing is caused by injecting a viscous fracturing fluid or a foam at a high pressure (hereinafter injection pressure) into the well to form a fracture. As the fracture is formed, the particulate material, referred to as a “propping agent” or “proppant” is placed in the formation to maintain the fracture in a propped condition when the injection pressure is released. Coated and/or uncoated particles are often used as proppants to keep open fractures imposed by hydraulic fracturing upon a subterranean formation, e.g., an oil or gas bearing strata. Particles typically used to prop fractures generally comprise sand or sintered ceramic particles as the fracture forms, the proppants are carried into the fracture by suspending them in additional fluid or foam to fill the fracture with slurry of proppant in the fluid or foam. Upon release of the pressure, the proppants form a pack that serves to hold open the fractures. Thus, the proppants increase production of oil and/or gas by providing a conductive channel in the formation. There is a need for a proppant carrier that can prevent settling of proppants or sand being positioned in the fractures.
During primary recovery a subterranean formation produces the oil by pressure depletion. In pressure depletion, the pressure difference between the formation and a production well or wells forces the oil contained within the formation toward a production well where it can be recovered. Typically, up to 35 percent of the oil initially contained in a formation can be recovered using pressure depletion. Methods have been developed to recover oil which could not be recovered using only pressure depletion techniques or secondary recovery techniques. These methods are typically referred to as “enhanced oil recovery techniques” (EOR).
One enhanced oil recovery process is referred to as surfactant flooding. This generally covers the use of an aqueous fluid containing surfactant injected into an oil rich formation to displace oil from the formation and the displaced oil is then recovered.
Another enhanced oil recovery process is referred to as chemical flooding. This generally covers the use of polymer and/or surfactant slugs. In polymer flooding, a polymer solution is injected to displace oil toward producing wells. The polymer solution is designed to develop a favorable mobility ratio between the injected polymer solution and the oil/water bank being displaced ahead of the polymer. In surfactant flooding, an aqueous solution containing surfactant is injected into the oil rich formation. Residual oil drops are deformed as a result of low interfacial tension provided by surfactant solution and drops are displaced through the pore throats and displaced oil is then recovered.
U.S. Pat. No. 4,432,881, incorporated herein by reference in its entirety, discloses an aqueous liquid medium having increased low shear viscosity as provided by dispersing into the aqueous medium (1) a water-soluble polymer having pendant hydrophobic groups, e.g., an acrylamide dodecyl acrylate copolymer, and (2) a water-dispersible surfactant, e.g., sodium oleate, or dodecyl polyethyleneoxy glycol monoether.
U.S. Pat. No. 4,541,935, incorporated herein by reference in its entirety, discloses fracturing processes which use aqueous hydraulic fracturing fluids. The fluids comprise: (a) an aqueous medium, and (b) a thickening amount of a thickener composition comprising (i) a water-soluble or water-dispersible interpolymer having pendant hydrophobic groups chemically bonded thereto, (ii) a nonionic surfactant having a hydrophobic group(s) capable of associating with the hydrophobic groups on said organic polymer, and (iii) a water-soluble electrolyte.
U.S. Pat. No. 5,566,760, incorporated herein by reference in its entirety, discloses a fracturing fluid comprising surfactants and hydrophobically-modified polymers.
U.S. Pat. No. 7,084,095, incorporated herein by reference in its entirety, discloses addition of polymers to a viscoelastic surfactant base system allows adjusting the rheological properties of the base fluid.
U.S. Pat. No. 7,427,583, incorporated herein by reference in its entirety, describes an aqueous viscoelastic fracturing fluid for use in the recovery of hydrocarbons. The fluid comprises a viscoelastic surfactant and a hydrophobically modified polymer.
U.S. Pat. No. 7,727,937 to Pauls et al, incorporated herein by reference in its entirety, discloses acidic treatment fluids used in industrial and/or subterranean operations, and more particularly, acidic treatment fluids comprising clarified xanthan gelling agents, and methods of use in industrial and/or subterranean operations.
U.S. Pat. No. 7,772,421 to Yang et al, incorporated herein by reference in its entirety, discloses a hydraulic fracturing composition comprising water, a pH responsive polymer and a proppant.
U.S. Pat. No. 7,789,160 to Hough et al, incorporated herein by reference in its entirety discloses an aqueous fluid useful for the recovery of crude oil from a subterranean formation, which includes a composition including a mixture of water, a water soluble block copolymer, an inorganic salt and at least one member of the group of a nonionic surfactant having an HLB of less than 12, and methods for using same.
U.S. Pat. No. 7,857,055 to Li et al, incorporated herein by reference in its entirety, discloses a fluid for treating a subterranean formation comprising an aqueous solution of a polysaccharide, a polyacrylamide, a crosslinking agent, and less than 0.1% by weight of any clay component, wherein the polyacrylamide is present in an amount of from about 0.01 percent to about 1 percent by weight of the fluid.
It would be desirable to provide stable fracturing fluids and EOR fluids for subterranean formations, such as natural gas and/or oil field.
Also, there is a need to enhance viscosity to improve personal care compositions. In personal care applications, consumers are increasingly demanding formulations that provide multiple benefits such as, but not limited to, unique sensory experience, enhanced moisturization, increased conditioning, improved delivery of active ingredients and compatibility. Synthetic rheology modifier polymers can be employed to assist in achieving one or more of these properties.
Also there is a need to enhance viscosity to improve cleaning compositions for home and industry.